U.S. Pat. No. 4,754,247 entitled "Molded Case Circuit Breaker Accessory Enclosure" describes a so-called "integrated" circuit breaker that provides both circuit interruption as well as accessory function. This Patent is incorporated herein for reference purposes and should be reviewed for its disclosure of an accessory cover mounted on the circuit breaker cover for providing access to field-installable accessory devices. The integrated circuit breaker includes an integrated circuit electronic trip unit which allows one circuit breaker design to be used over a wide range of ampere ratings in combination with the rating plug, also mounted in the circuit breaker cover. The electronic trip unit is described within U.S. Pat. No. 4,589,052 and the rating plug is described within U.S. Pat. No. 4,649,455 both of which are incorporated herewith for reference purposes.
When such circuit breakers are used within higher ampere-rated industrial applications, a pair of contacts are employed within each phase of the electrical power distribution circuit for efficient operation during quiescent conditions and for rapid circuit interruption upon the occurrence of predetermined overcurrent conditions. U.S. patent application Ser. No. 330,521 entitled "Molded Case Circuit Breaker Movable Contact Arm Arrangement" describes one such circuit breaker and is incorporated herein for reference purposes. When such contacts become separated upon short circuit overcurrent conditions, highly ionized arcs occur that generate arc gases which must be controllably released from the circuit breaker enclosure to prevent damage to the circuit breaker enclosure without incurring extraneous electrical conduction outside the circuit breaker enclosure. An efficient arc chute arrangement for controlling the release of arc gases is described within U.S. patent application Ser. No. 344,936 entitled "Compact Current Limiting Circuit Breaker", which Patent Application is incorporated herein for reference purposes.
U.S. patent application Ser. No. 292,717 entitled "Molded Case Circuit Breaker Line Strap Configuration" describes the cooperation between the circuit breaker line straps and the circuit breaker case to prevent egress of ionized gases in the vicinity of the line strap terminals.
The instant invention relates to means for guiding the motion of a pair of movable contact arms upon the occurrence of overcurrent conditions and also relates to separate means for controlling the safe release of arc-generated exhaust gases to the exterior of the circuit breaker enclosure.